Polyacrylic Acid Superplasticizer Synthesis And Modification

Polycarboxylate superplasticizers have many virtues, such as high rangle water-reducing rate and good controlling of concrete slump.The main work of this thesis include:1. Polyoxyethylene fatty acids and excessive unsaturated acid were esterified at 100～110℃, and esterification macromonomer was obtained and the effect of the alcohol polyoxyethylene chain length on esterification was discussed as well. The results showed: with polyoxyethylene chain length increasing, esterification rate decreased significantly. Used p-toluenesulfonic acid as the catalyst, AEO-3 needs 2.5 hours, AEO-25 requires 6.5 hours, with the esterification ratio of 100%.With esterification macromonomer prepared above, Sodium methyl acryl sulfonate (SAS), acrylic acid (AA) used as raw materials, polymerization was proceeded in aqueous solution. The best polymerization conditions were 80℃and 5 hours, the best amount of initiator was 2.5%～5.0% of total quality of monomers.The effect of the amount of AA, SAS and polyoxyethylene fatty acids on superplasticizer performance were discussed. The results showed that when the sulfonic monomer, carboxyl monomer and polyoxyethylene large molar were n₁ =3, n₂=7. n₃=1, the dispersion property of polyacrylic acid was better. When the content of polyacrylic acid superplasticizer was 0.45%, fluidity of cement paste could reach 270mm.2. Using 2-acrylamido-2-methyl acrylic acid (AMPS) replacing part amount of SAS and another macromonomer M replacing alcohol polyoxyethylene ether to improve superplasticizer, we found that the property of modified superplasticizer were improved significantly. Through orthogonal experiments, the best monomer ratio was obtained: SAS:AMPS:AA:M=1.5:2:7:1(M molecular weight was 1500 and 1000 and the 50% component). In this ratio superplasticizer has excellent dispersion and dispersion properties. With the amount of 0.2%, 0.3%, the fluidity could reach 225mm and 275mm.These synthesized polyacrylic acid superplasticizers have certain retarding of cement, the water-reducing rate, strength and workability were nearly equal to other domestic polycarboxylate superplasticizer, but have certain distance to similar foreign polycarboxylate superplasticizer performance.